alembic.operations.Operations

class alembic.operations.Operations(migration_context: MigrationContext, impl: Optional[BatchOperationsImpl] = None)

Define high level migration operations.

定义高级迁移操作。

Each operation corresponds to some schema migration operation, executed against a particular MigrationContext which in turn represents connectivity to a database, or a file output stream.

每个操作对应于一些模式迁移操作，针对特定的 MigrationContext 执行，而后者又表示与数据库或文件输出流的连接。

While Operations is normally configured as part of the EnvironmentContext.run_migrations() method called from an env.py script, a standalone Operations instance can be made for use cases external to regular Alembic migrations by passing in a MigrationContext:

虽然 Operations 通常配置为从 env.py 脚本调用的 EnvironmentContext.run_migrations() 方法的一部分，但可以通过传入 MigrationContext 为常规 Alembic 迁移之外的用例创建独立的 Operations实例：

from alembic.migration import MigrationContext
from alembic.operations import Operations

conn = myengine.connect()
ctx = MigrationContext.configure(conn)
op = Operations(ctx)

op.alter_column("t", "c", nullable=True)

Note that as of 0.8, most of the methods on this class are produced dynamically using the Operations.register_operation() method.

请注意，从 0.8 开始，此类中的大多数方法都是使用 Operations.register_operation() 方法动态生成的。

Construct a new Operations

构建一个新的 Operations

参数:

migration_context – a MigrationContext instance. (一个 MigrationContext 实例)